Today there is a growing need to provide controlled access and vessel management during such procedures as stenting, atherectomy or angioplasty. Generally during these procedures there is a high opportunity for the release of embolic material. The emboli may travel downstream from the occlusion, lodging deep within the vascular bed and causing ischemia. The resulting ischemia may pose a serious threat to the health or life of a patient if the blockage forms in a critical area, such as the heart, lungs, or brain.
Several previously known methods and apparatus incorporate the use of an external suction system in conjunction with an aspiration catheter for removal of the clot and/or removal of embolic particles. However, several disadvantages arise when using an external suction system as the sole means for flow management within a vessel. First, it may be difficult to establish the proper aspirating pressure required at the treatment site, and external pressure adjustments used with suction pumps may lead to an incorrect amount of suction for a given set of circumstances. If the amount of suction is too low for the circumstances, then embolic particles may not be effectively removed and may travel downstream from the original occlusion, leading to further occlusive events. If the amount of suction is too high, the vessel may collapse.
Moreover, if an external suction pump is utilized, retrieval of downstream emboli may require a flow rate that cannot be sustained by the vessel wall for more than a few seconds, resulting in insufficient removal of emboli. Additionally, continuous use of an external suction pump may result in excessive blood loss, requiring infusion of non-autologous blood and raising related safety issues.
Other methods for embolic removal have relied on more natural aspirating effects. For example, previously known devices have relied on the pressure differential between the atmosphere and blood flow in a treatment vessel to cause a reversal of flow in the treatment vessel. However, such natural aspiration techniques may provide insufficient flow to effectively remove emboli.
In view of these drawbacks of previously known systems, it would be desirable to provide a proximal catheter assembly that allows a catheter to achieve a substantially continuous level of natural, physiologically-regulated aspiration through a working lumen of the catheter.
It also would be desirable to provide a proximal catheter assembly that provides an appropriate level of retrograde flow at a treatment site to direct dislodged particles into a catheter for efficient removal without damaging the treatment vessel.
It further would be desirable to provide a proximal catheter assembly that provides an external suction/infusion port that selectively may be used, in conjunction with natural aspiration techniques, to further influence flow in a treatment vessel.
It still further would be desirable to provide a proximal catheter assembly that allows emboli to be filtered and blood reperfused into a patient's vessel to reduce blood loss.
It also would be desirable to provide a proximal catheter assembly that is configured to minimize “back-bleed” that occurs when flow exits through a hemostatic port disposed at the proximal end of a catheter.
It also would be desirable to provide a proximal catheter assembly having a relief valve that is configured to regulate the level of suction-assisted aspiration that may be provided through the working lumen of the catheter.